Chromatographic apparatus



Sept. 12, 1967 R. H. POWELL CHROMATOGRAPHIC APPARATUS I5 Sheets-Sheet 1 Filed Feb. 23, 1965 p R. H. POWELL 3,341,017

} CHROMATOGRAPHIC APPARATUS Filed Feb. 23, 1965 3 Sheets-Sheet 2 R. H. POWELL GHROMATOGRAPHIC APPARATUS Sept 12, 1967 a Shets-Sheet 3 Filed Feb. 23, 1965 F/G.5. F

United States Patent "ce 3,341,017 CIHROMATOGRAPHIC APPARATUS Robert Henry Powell, Kenley, Surrey, England, assignor to Shandon Scientific Company Limited, London, England, a British company Filed Feb. 23, 1965, Ser. No. 434,477 19 Claims. (Cl. 21094) This invention relates to chromatography and is more specifically concerned with improved apparatus for carrying out ascending or descending chromatography.

In ascending or descending chromatography chemical substances are separated and are identified by a moving solvent on a sheet of bibulous material. The sheet is nearly always a filter paper although it has been proposed to use a sheet of bibulous material deposited as a thin layer on an inert surface. For simplicity the term sheet has been used throughout this specification to denote the bibulous material and it is to be understood as covering not only paper but also other forms of bibulous material, such as the above-mentioned thin layer, on which a chromatographic run may be performed.

A drop taken from a liquid mixture of the substances to be separated is placed or spotted near one end of the sheet. The drop is allowed to dry, leaving a spot of the mixed substances. The sheet is then arranged vertically in a tank and either the upper or lower end of the sheet is immersed in a trough containing solvent without actually immersing the spot itself. In ascending chromatography the lower end of the sheet is dipped into the trough so that the solvent travels upwardly, whereas in descending chromatography the upper end of the sheet is immersed in the solvent which travels downwardly through the sheet. In some cases a vessel is used instead of a trough when carrying out ascending chromatography, and the term trough is to be understood throughout the specification as including a vessel.

During the chromatographic run the solvent from the trough flows through the sheet by capillarity, over and past the spot. As it flows, it dissolves and carries along the substances from the spot, each substance generally moving at a different rate from the others. At the end of a suitable length of time the sheet is removed from the trough and dried and the separated substances are observed immediately, if colored, and if invisible they may generally be made visible by suitable treatment or radiation.

Unsatisfactory separations and poor results. may be experienced if the chromatographic run is carried out in a changing environment. For this reason the sheet is normally mounted inside a tank provided with a lid which is closed during the run and during a period prior to commencement of the run necessary to ensure that equilibration has been reached inside the tank. Equilibration is necessary because a mixed solvent introduced into the tank commences to evaporate and during the evaporation the vapor composition in the tank gradually changes. Eventually a condition is reached where the atmosphere in the tank is saturated at the prevailing temperature with the partial vapor pressures of each of the solvent constituents. When this condition is reached the tank and the sheet within it are said to have reached equilibration. Equilibration may take some hours depending on. the vapor pressures of the solvent constituents and also on the prevailing ambient temperature.

Equilibration is carried out, in practice, by introducing into the tank the dried spotted sheet in the position in which it is to be used some time before the run is actually commenced. The empty solvent trough which is to be filled with solvent at the commencement of the run is also introduced into the tank at this time and a small quantity of the solvent is poured into the bottom of the 3,341,017 Patented Sept. 12, 1967 tank where it is out of direct contact with the sheet. Finally a grease-sealed lid is placed on the tank and a 'suflicient time is allowed for equilibration to have been achieved.

To commence the run a quantity of solvent at the same temperature as the vapor inside the tank is introduced into the solvent trough. This is commonly done by removing the lid. Preferably, however, removal of the lid after equilibration is avoided by providing the lid with holes which are normally closed by stoppers. When 7 equilibration is complete the stoppers are removed and solvent is poured via the holes in the lid into the trough. The stoppers are then replaced.

These methods of performing a chromatographic run have two serious disadvantages. The first disadvantage is that one can never be quite sure that the solvent added to the tank to commence the run is at precisely the same temperature as the inside of the tank and any temperature difference will alter the conditions inside the tank so that the chromatographic run will be performed in a changing environment. The second disadvantage is that it is virtually impossible to ensure that when the solvent is added to the tank at the commencement of a run, none of the atmosphere surrounding the tankis introduced into the tank also so that equilibration is disturbed. Naturally when the solvent is added by way of holes through the lid the volume of surrounding air introduced into the tank is very much smaller than when the tank lid is removed, but nevertheless there is some change in the conditions inside the tank.

One object of this invention is the provision of improved chromatographic apparatus.

Another object of this invention is the provision of chromatographic apparatus which is automatically operated.

Another object of this invention is the provision of chromatographic apparatus which does not require the addition of solvent from an external reservoir after equilibration.

Another object of this inveition is the provision of chromatographic apparatus which is automatically controlled but does not utilize valves.

A further object of this invention is the provision of chromatographic apparatus readily adaptable for ascending or descending chromatography.

, A further object of this invention is the provision of chromatographic apparatus able to perform a plurality of runs simultaneously.

Another object of the invention is the provision of compact, readily adjustable timing mechanism for controlling a chromatographic run.

A further object of the invention is the provision of descending chromatographic apparatus in which more solvent is used than can be held in the solvent trough, without the requirement of having to add new solvent to the tank sometime during the run.

Yet another object of the invention is the provision of chromatographic apparatus which is simple to clean, set up and use.

These and other objects of the invention will be apparent from the following description of embodiments of the invention.

In one form of the invention apparatus for carrying out ascending or descending chromatography is constituted by: a tank closable by a lid; a trough for mounting in the tank and for receiving solvent at the beginning of a chromatographic run; an element for holding a spotted sheet of bibulous material in the tank with a portion dipping into the trough, a cistern mountable inside the closed tank and for holding liquid solvent required for the run during equilibration; and a timing mechanism operatively connected to empty the cistern, after a chosen equilibration period, so that the liquid solvent flows gradually from the cistern into the trough to commence the run.

The term gradually is used throughout this specification to mean that the discharge of solvent from the cistern, when full, into the trough takes place sutficiently smoothly for any sudden surge of liquid to be avoided. Thus any surge which would be produced by suddenly emptying into the solvent trough a reservoir of solvent so that it discharges its entire volume of solvent in a second or so is not experienced in the present invention yet the advantages of having the solvent inside the closed tank during the equilibration period are obtained. The rate of discharge of solvent from the cistern into the trough is, of course, greater than the rate of removal of solvent from the trough by capillary action in the bibulous material.

Preferably the use of complicated electrically operated valves with their attendant fire hazard in the presence of highly inflammable organic liquid vapors is avoided by so designing the cistern that, to commence the run, it is moved from a first position at which it holds the solvent to be used, to a second position at which the solvent discharges gradually into the trough. In a preferred arrangement, the cistern is mounted on trunnions and is rotatable by the timing mechanism about an axis defined by the trunnions. The cistern is suitably provided with two openings which are normally located above the level of held solvent when the cistern is at said first position. To commence the run the cistern is rotated so that the openings are moved to its underside and allow the solvent to discharge gradually into the trough. One of said openings comprises a solvent outflow hole which, conveniently, has its axis inclined to the rotational axis of the cistern. The other hole may comprise the flared mouth of an air inlet pipe which extends into the cistern and has its open inner end at a level above the level of the contained solvent when the cistern is moved to said second position. The air inlet pipe allows air to enter the cistern and replace the volume of solvent discharged through the solvent outflow hole.

The timing mechanism suitably comprises a modified alarm clock. In one arrangement a member is lifted by the alarm hand. The member may be connected by a cord extending through a hole in the lid of the tank to the cistern where the cord is wrapped around the body of the cistern so that lifting of the member causes the cistern to rotate through 180 thereby bringing the solvent outflow hole beneath the level of solvent in the cistern. Conveniently the member is fixed at the free end of a lever pivoted at one end and having a pin intermediate its ends which extends through an elongated slot in a hanging link pivoted at its upper end to a gear wheel which rotates when the alarm is set off. During the equilibration period the lever is in its lower position and, when the alarm is operated, the lever is lifted by the hanging link to its upper position at which it may be held by a magnet so that the alarm can run down.

The invention will now be described in more detail, by way of examples, with reference to the accompanying drawings, in which:

FIGURE 1 is a perspective view, with parts broken away for the sake of clarity, of a tank in which an ascending chromatographic run is to be performed;

FIGURE 2 is an exploded view of the contents of the upper portion of the tank having troughs for descending chromatography;

FIGURE 3 is a sectional side view of one construction of cistern mounted on a trough containing a paperweight element and used for descending chromatography;

FIGURE 4 is a view corresponding to FIGURE 3 but showing another construction of cistern;

FIGURE 5 is a side view of a timing mechanism; and,

FIGURE 6 is a rear view of the timing mechanism with the back cover removed to show working details.

The apparatus which may be used to carry out either ascending or descending chromatography, comprises an upright tank 1 of rectangular cross-section, made of glass and of overall size 14 /2 inches long, 9 inches wide, and 22 /2 inches deep. The tank has end-walls 2 provided close to their upper ends with outwardly directed flanges 3 integrally formed inside the tank with shouldered portions 4 providing ledges. The top of the tank 1 is closed by a lid 5 in the form of a flat glass cover plate. The mating surfaces of the lid and tank are ground flat and normally an inert grease seal is formed between them to make a gas-tight joint.

The top shoulders 4 are designed to support opposite ends, respectively, of different components arranged sideby-side in the top of the tank. Each shoulder 4 is provided with six semi-cylindrical recesses 7 (see FIGURE 2) for receiving the ends of rods 8. Four of the rods 8 are anti-Syphon rods, and the two remaining rods are for supporting drape papers down the sides of the tank to provide an extended evaporating surface for promoting equilibration. Disposed between the three pairs of grooves are two rebates 10 of channel form each for accommodating a flat 11 formed in the underside of each end of each of two glass solvent troughs 12. Between the flats 11 each trough is provided with a rounded floor 13.

The rounded floor 13 of the trough is provided at one end with a downwardly projecting tubulure 14. This is connectable by an inert plastics sleeve to a connection tube 15 which extends downwardly to a second trough 16 located on the floor of the tank 1. If the tank is required for descending chromatography the trough 12 is replaced by another trough 12' (shown in FIGURE 3) which is identical to the trough 12 except for the omission of the tubulure 14. The connection tube 15 and free-standing trough 16 are not used for descending chromatography and are omitted also.

Returning to FIGURE 1 the trough 16 is free-standing in a pool of solvent on the floor of the tank for equilibration purposes. The top edge 17 of the trough is headed and is formed, at each end of the trough, with a V-shaped indentation or notch 20.

The troughs 12 and 12 are each adapted to serve as a mount for a rotatable cistern 21 as shown in FIG- URE 3. The cistern 21 comprises a cylindrical glass tube which tapers at opposite ends into trunnions 23 coaxial with the tube. The trunnions are integrally made with the glass tube and are button-ended to provide slightly enlarged ends 24 which project slightly beyond the adjacent end-walls 18 of the trough. Each trunnion rests in one of the notches 20. As shown in FIGURE 1, the cistern is carried lengthwise above the trough and is of lesser diameter and length than the width and length of the trough respectively. The top of the cistern, as shown in FIGURE 3, is formed with an anchorage 25 provided by a depression in the wall of the cistern spanned by a glass bridge 26. The top of the cistern is also provided at one end with a solvent outflow hole 27 and at the other end with the flared mouth of an air inlet pipe 28 extending diametrically through the interior of the cistern and terminating close to the opposite wall. The solvent outflow hole 27 is formed by an open ended flute 30 pressed inwardly of the wall of the cistern to provide a solvent outlet having an axis inclined to the rotational axis of the trunnions 23. By inclining the solvent outflow hole in this manner it has been found that the risk of its being closed by a surface tension film is negligible, and also the direction of initial outflow from the cistern into the empty trough tends to be axially and not radially so that rapid longitudinal distribution of solvent takes place in the trough with more uniform paper-wetting. The air inlet pipe 28 at the other end of the cistern is sufliciently long to provide a sufficient head of liquid when the cistern is rotated through to disrupt any surface tension film across the solvent outflow hole 27. In practice an air inlet pipe of about 1 inch in length is suflicient for this purpose.

Lying on the fioor 13 of the trough 12' is a paper weight formed by a glass-sheathed metal rod 31. Opposite ends of the rod sheathing are concave to enable'them to be grasped securely between the fingers when placing the paper weight in position in the trough and removing it from the trough after use. During ascending chromatography the paper weight is not used as the sheet is suspended by metal clips from one of the rods 8 and dips into the lower free-standing trough 1-6. However during descending chromatography, when the solvent flows downwardly past the spot, the upper end 9 of the sheet is passed over the adjacent anti-syphon rod 8 and the side wall of the trough and is held against the floor of the trough by the weight of the glass-sheathed rod 31. The parts are so dimensioned that the sheet does not come in contact with the cistern 21.

Mounted on top of the lid 5 is a timing mechanism 40 having a clock face provided with an alarm hand 41. The timing mechanism comprises a modified alarm clock. The extent of the modification will be apparent by referring to FIGURES 5 and 6. Referring first to FIGURE 6 the alarm clock is provided with a main gear wheel 42 which rotates during winding and unwinding of the alarm. A hanging link 43 is pivotally connected at 44 close to the periphery of the gear wheel 42. An elongated slot 45 is provided in the lower portion of the hanging link 43 to receive a pin 46 fixed to one side of a lever arm 47.The arm 47 is pivoted at one end 48 inside the clock and its other end projects through a slot 50 in the wall of the clock and carries at its outer end a double-ended member 51. The lever arm 47 is provided inside the clock with an armature 52 which, when the lever arm is in its upper position shown in dotted outline, co-operates with a fixed permanent magnet 53 to hold magnetically the arm 47 in its raised position. The double-ended member 51 comprises a metal tube having in each end the body of a headed stud 55 forming a clamp. A compression spring (not shown) inside the tube 51 provides a bias against which the stud 55 can be finger pressed. The end of the tube 51 is formed with an axial slot 56 for guiding a pin 57 on the body of the stud 55. Adjacent each stud 55 the tube is formed with an oblique slit 58 which may be registered with a similar oblique slit (not shown) in the body of the stud when it is pressed inwardly against the bias to open the clamp. On release of the stud to close the clamp the two slits move out of register with one another. An adjustable stop 60 is located at the lower end of the slot 50 to limit downward movement of the arm 47 and so enable the lift of the member 51 to be varied to suit cisterns of different diameters.

Referring to FIGURE 1 it will be seen that the length of the member 51 is sufiicient for each of the clamps formed by the spring biased studs 55 to be located above each of two apertures 61 formed in the glass lid 5. A cord 62 may be clamped to either end of the member 51 and passed through the aperture 61 and around the body of the cistern 21 the other end of the cord or preferably its mid-point being tied to the anchorage 25. The length of the stroke of the member 51 is equal to half the circumferential length of the cistern 21 so that movement of the member 51 between its lower and upper positions is accompanied by rotation of the cistern through 180.

The apparatus is used as follows:

For ascending chromatography the free-standing trough 16 is placed in the bottom of the tank 1 as shown in FIGURE 1 and the troughs 12 and anti-syphon rods 8 are mounted in the rebates and the recesses 7, respectively, formed by the shoulders 4. The connection tubes are of course connected at'their upper ends to be tubu lures 14 of the troughs so that their lower ends dip into the free-standing troughs 16 as previously described. For descending chromatography the free-standing troughs are dispensed with and the troughs 12 replace the troughs 12.

Drape papers (not shown) are suspended over the outermost syphon rods 8 so that their lower ends touch the floor of the tank on which a pool of solvent is placed for equilibration purposes. The or each spotted sheet on which the run is to be performed is next placed in position. If an ascending chromatographic run is to be performed the sheet is held upright in the tank with the end portion adjacent the spot dipping into the trough 16. If a descending chromatographic run is to be performed the sheet is arranged so that its end portion adjacent the spot dips into the trough 12' and the remainder of the sheet is allowed to hang freely vertically in the tank. In the case of a descending chromatographic run the paper weight 31 holds the end 9 of the sheet in the trough 12'. It will be appreciated that two runs may be performed simultaneously from the same trough 12 and, by the use of two troughs, four runs may be performed simultaneously. The cistern 21 may be filled with solvent through the air inlet pipe 28. During filling the displaced air leaves through the solvent outlet hole 27. Filling may be facilitated by the use of a squeeze bottle.

Before the cistern 21 is filled the cord 62 is tied to the anchorage 25 and each end passed in opposite directions once around the body of the cistern which after filling is then placed in position above one of the troughs 12, as shown in FIGURE 3, so that its trunnions rest in the notches 20. With both cisterns in position the lid 5 is placed over the top of the tank and both ends of each of the cords 62 are passed through the respective apertures 61. Stoppers (not shown) provided with small holes may be threaded onto the ends of the cords to close the apertures 61.

The clock of the timing mechanism is first wound. The alarm hand is then set at the time less than twelve hours ahead at which it is intended that the chromatographic run should start. The alarm key is then wound a sufficient number of turns depending on the load to be moved, whether one cistern or two cisterns. During the final partial turn the member 51 is lightly pressed downwards with the finger and this partial turn is stopped when the lever arm 47 is in its lower-most position.

The timing mechanism is then placed on top of the lid 5 so that the clamps at the end of the member 51 overlie the two apertures 61. One end of each cord is gently drawn upwardly through the apertures so that all slack is removed and the opposite end of each cord is held just taut to prevent unwanted rotation of a cistern and premature discharge of its contents. One end of each cord is gripped in an individual one of the clamps at the ends of the member 51. This is easily accomplished by pressing the studs inwardly so that their slits register with the slits 58 in the ends of the member 51 and'placing the cord into the registering slits. The pressure on the studs is then released so that the cord is firmly gripped.

At the time set by the alarm hand 41 the alarm operates and, referring to FIGURE 6, the swinging link 43 is raised to lift the memberSl and cause each of the cisterns to rotate simultaneously through This rotation brings the solvent outlet hole 27 and the mouth of the air inlet pipe 28 to the underside of the cistern and allows the solvent to discharge gradually into the trough. Because ,the mouth of the air inlet hole and the outflow hole 27 are located beneath the rim of the trough it is impossible for the trough to overfill. Nevertheless the volume of sol- ,vent used for carrying out the run can exceed the volume of the trough because as soon as the solvent level in the trough falls beneath the level of the outlet hole 27 and the mouth of the air inlet pipe 28, more solvent enters the trough until they are once again closed. Thus it will be appreciated that throughout the run, with the exception of the end period, the solvent level in the trough is constant. Of course it will be appreciated that this is only 'true for descending chromatography as, for ascending chromatography the entire volume of the solvent in the 7 cistern 21 is discharged gradually through the connection tube 15 to the free-standing trough 16.

Other constructions of cistern to that shown in FIGURE 3 are possible. FIGURE 4 shows such an alternative form of construction. Here, the anchorage for the cord is provided by an apertured lug 80 formed in the glass wall of the cistern. It will also be seen that the air inlet pipe 28 is cut obliquely at its inner end to reduce any risk of its being closed by a surface tension film. The solvent outflow hole 27' is formed by a simple circular aperture between A1 and /s inch diameter in the wall of the cistern. The trough used with this construction of cistern is also slightly modified in that the indentations 68 at opposite ends of the trough are of channel shape. One of the trunnions 70 is provided with a flat 71 which, when the cistern is in the first position (shown), rests on the fiat floor of the indentation 68 to locate the cistern correctly with its solvent outlet uppermost.

Only a small amount of the solvent is discharged into the trough during initial rotational movement of the cistern, this small amount corresponding to the solvent previously held in the air inlet pipe 28. However once the cistern has rotated through a full 180 the length of the air inlet pipe 28 is suflicient to provide enough solvent pressure in the cistern to disrupt any surface tension film across the solvent outlet hole 27'.

From the above description of embodiments of the invention it will be appreciated that the applicant has devised apparatus which has all of the advantages of prior art apparatus without the disadvantages. Further, the versatility of the apparatus is such that it is able to perform ascending or descending chromatography and to be automatically controlled by a timing device. Moreover, in the case of descending chromatography, the run can be performed with more solvent that the trough is designed to hold and with a constant level of solvent throughout the major part of the run. Finally, all of the parts of the apparatus in contact with the solvent are of glass so that they are not attacked by solvents or acids, and the use of expensive electrically operated valves to control solvent flow is avoided with the constructions shown in the particular embodiment described. It is to be understood that the invention is not limited to the use of a movable cistern, as other means for discharging the solvent from the cistern into the trough to commence the chromatographic run may be used.

I claim:

1. Chromatographic apparatus comprising a tank, a lid for closing said tank, a solvent trough mounted in said tank, support means in the upper portion of said tank, an element carried by said support means, a spotted sheet of bibulous material held in said tank by said element and having a portion dipping into the solvent trough, a solvent cistern carried by said support means above the trough and holding solvent during equilibration, a timing mechanism mounted outside said tank, a member moved by said timing mechanism after a predetermined time lapse for equilibration, and means operatively connecting the member to discharge held solvent gradually from the cistern into the trough to commence a chrmatographic run.

2. Apparatus according to claim 1, in which said cistern comprises a rotatable hollow vessel having two openings located above the solvent level in the cistern during equilibration but movable by rotating the cistern to beneath the solvent level to discharge solvent gradually from one opening while tank atmosphere is admitted to take its place through the other opening.

3 Apparatus according to claim 1, in which the said solvent trough is free-standing on the tank floor.

4. Apparatus according to claim 1, in which the solvent cistern is mounted on the solvent trough and is rotatable by said operatively connecting means from a first position at which solvent is held during equilibration, to a second position at which solvent is discharged gradually into the trough.

5. Apparatus according to claim 1, in which said element comprises a glass rod having concave ends and fitting into the trough, the rod containing a metal core.

6. Chromatographic apparatus comprising a tank, an apertured lid closing said tank, a solvent trough mounted inside the upper portion of said tank, an element mounted in the trough, a spotted sheet of bibulous material suspended in the tank and having one end portion held in the trough by said element, trunnion supports at opposite ends of the trough, trunnions resting on said supports in axial alignment, a. solvent cistern rotatably carried between said trunnions and overlying said trough, a timing mechanism on said lid, a member movable by said timing mechanism after a predetermined time lapse for equilibration, means passing through the aperture in the lid and connecting said member to said cistern to rotate said cistern after said time lapse to discharge solvent gradually from the cistern into the trough to commence a chromatographic run.

7. Apparatus according to claim 6, in which said cistern comprises a cylindrical chamber having a horizontal axis and a solvent discharge hole in one side, the underside of the chamber dipping into the trough.

8. Apparatus according to claim 6, in which the cistern comprises a cylindrical chamber having a solvent discharge hole formed in one side and part of its undersurface dipping into the trough, the element being located between the cistern underside and the trough floor and comprising a rod having concave ends and formed by a glass-sheathed metal weight.

9. Apparatus according to claim 6, in which the cistern comprises an axially horizontal chamber formed in one side with a solvent outflow hole and a mouth of an air entry pipe which extends diametrically through the chamber and terminates close to the opposite inside wall.

10. Chromatographic apparatus comprising a glass floor and opposed side walls defining a tank, a glass lid closing said tank, a free-standing solvent trough on the floor of said tank, support surfaces integrally formed in the upper portions of one pair of opposed side walls, an element mounted inside the tank and having opposite end-portions resting on said support surfaces, a spotted sheet of bibulous material hanging from said element and having its lower end dipping into the said trough, a glass cistern-support trough resting at opposite end-portions on said support surfaces, tubular means communicating with said cistern-support trough and extending downward and into said free-standing trough, a glass cistern carried above said cistern-support trough and carrying solvent during equilibration, a timing mechanism mounted outside the tank, a member movable by said timing mechanism after a predetermined time lapse for equilibration, and means operatively connecting the member to the cistern to move it after equilibration from a solvent-holding position to a solvent-discharge position to discharge the held solvent into the support trough and via said tubular means to the free-standing trough to commence the chromatographic run.

11. Apparatus according to claim 10, including parallel glass anti-Syphon rods resting at opposite ends on said support surfaces and disposed on each side of said cistern supporting trough.

12. Apparatus according to claim 10, including a glass tubulure extending downwards from the underside of the cistern-supporting trough, and a detachable glass tube extending downwards from the tubulure to the freestanding trough.

13. Chromatographic apparatus comprising a glass tank, a glass aperture lid closing said tank, a solvent trough mounted inside said tank, element-support means in the upper region of said tank, an element carried by said support means, a spotted sheet of bibulous material h ld i l an pright. position in the tank from its upper end by said element and having a portion dipping into 'by the alarm hand, and a cord passing through the aperture lid and connecting the member to the lug on the cistern, the portion of the cord adjacent the lug passing around a cylindrical surface of the cistern which is concentric with the axis of rotation of the cistern.

14. Apparatus according to claim 13, including two solvent troughs and two cisterns arranged side-by-side and each associated with one solvent trough, the two cisterns being operatively connected through the glass lid to the member of the timing mechanism.

15. Apparatus according to claim 13, in which the cistern comprises a closed glass chamber having axially aligned trunnions extending from opposite end-portions and carried on bearings formed on two spaced trough ends, the cistern overlying the trough of which the trough ends form part.

16. Chromatographic apparatus comprising a tank, a lid closing said tank, a solvent trough in said tank, support means inside said tank, a solvent cistern carried inside the tank by said support means and holding solvent during equilibration, a timing mechanism mounted outside the tank, a casing enclosing said timing mechanism and formed with an upright slot, a clock face on said timing mechanism, an alarm hand on said close face, an alarm unit in said timing mechanism, a vertical wheel rotated by said alarm unit at the time signified by said alarm hand, an eccentric pivot pin on said wheel, a link hanging on said pivot pin and formed with an elongated slot in its lower portion, a vertically movable lever pivoted at one end inside the casing and having its other end protruding through the upright slot in the casing, a second pin fixed to the lever intermediate its ends and passing through the slot in the hanging link, and means operatively connecting the protruding end of the lever to the interior of the tank to discharge held solvent from the cistern into the trough after a predetermined time lapse for equilibration and determined by the setting of the alarm hand.

17. Apparatus according to claim 16, in which said operatively connecting means includes a cord, and a cord clamp fixed to a member on the protruding end of said lever.

18. Apparatus according to claim 16, in which said operatively connecting means includes a horizontal member fixed intermediate its ends to the protruding end of said lever and having at each end a cord clamp resiliently biased to its clamping position.

19. Apparatus according to claim 16, including a vertically adjustable stop in the casing at the lower end of the upright slot for controlling the lower position of the lever, and a magnetic member positioned to hold the lever magnetically in its upper position in the slot and mounted inside the casing in the path of movement of a magnet part on the lever.

No references cited.

SAMIH N. ZAHARNA, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,341,017 September 12, 1967 Robert Henry Powell It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

5 Llinthe heading (13(1) the printed specification, between lines an insert aims priorit a lication Great B Feb. 24, 1964, 7547/64 y pp rltaln Signed and sealed this 23rd day of September 1969.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, J r.

Commissioner of Patents Attesting Officer 

1. CHROMATOGRAPHIC APPARATUS COMPRISING A TANK, A LID FOR CLOSING SAID TANK, A SOLVENT TROUGH MOUNTED IN SAID TANK, SUPPORT MEANS IN THE UPPER PORTION OF SAID TANK, AN ELEMENT CARRIED BY SAID SUPPORT MEANS, A SPOTTED SHEET OF BIBULOUS MATERIAL HELD IN SAID TANK BY SAID ELEMENT AND HAVING A PORTION DIPPING INTO THE SOLVENT TROUGH, A SOLVENT CISTERN CARRIED BY SAID SUPPORT MEANS ABOVE THE TROUGH AND HOLDING SOLVENT DURING EQUILIBRATION, A TIMING MECHANISM MOUNTED OUTSIDE SAID TANK, A MEM- 